The specific aims of this research proposal are to determine the effects that the anticonvulsants phenytoin, carbamazepine, valproic acid, ethosuximide, acetazolamide, and diazepam have on cation and anion transport processes and intracellular pH homostasis of glial cells isolated from the cerebral cortices of 3-day old neonatal rats and maintained in isolated tissue culture. They include determination of the acute and chronic effects of each agent on: (1) the DNA and protein content of treated cultures, (2) the activity of the transport enzymes Na+/K+, Ca++/Mg++, and HCO3-ATPase, (3) the concentration of intracellular Na+, K+, and Cl, and ion flux measurements, (4) the activity of the glial specific enzyme carbonic anhydrase, (5) the membrane potential, resistance and conductance, (6) the intracellular pH, (7) the effect of specific inhibitors of cation and anion transport in the presence and absence of anticonvulsant drugs, (8) the effect of increasing extracellular K+, and (9) the effect of pentylenetetrazol alone and with each anticonvulsant agent. These studies will involve the disiplines of neuropharmacology, biochemistry, electrolyte and acid-base chemistry, eletrophysiology, cellular biology, and isolated tissue culture. The experiments are designed to test the hypothesis that changes in these parameters will enhance glial cell regulatory process thereby providing the CNS with an enhanced ability to regulate the extracellular fluid. Such experiments are important, for if a thorough understanding of the mechanisms of these drugs is to be obtained, a comprehensive examination of their effects on glial cells as well as neurons must be undertaken. When the mechanisms of these anticonvulsants are determined, new drugs exhibiting similar characteristics but with fewer side-effects can be made and tested for clinical efficacy.